Fires on Governors Island could burn unchecked for half an hour or more before help arrives.

That is one revelation in the F.D.N.Y.’s new operations plan for the island, which was finished Jan. 27, 10 days after the city closed the island’s firehouse. The plan details the many obstacles Lower Manhattan firefighters will face from the time an alarm sounds to the time they reach the fire and put it out, from absent ferries to low water pressure in the island’s hydrants.

“It’s not good,” said Rob Pirani, executive director of the Governors Island Alliance, after hearing a presentation on the plan.

The city closed the Governors Island firehouse to save about $1 million a year. The city also closed four other fire companies only at night, including Engine 4 on South St., which saved an additional $7.9 million.

Governors Island has no residents, but the island attracted more than 100,000 visitors last summer, and construction happens year-round. Future plans for the island include an artist residency program and a public high school.

The Governors Island closure is not permanent — the Fire Dept. will staff the island whenever 100 or more people are on it, meaning every weekend over the summer and every weekday once the New York Harbor School opens in the fall of 2010. But every night once the visitors have gone home, and every day this winter as construction on the island continues, and firefighters will be a boat ride away.

The city decided to close the firehouse because the three firefighters that staffed it responded to very few calls — only 10 emergencies in 22 months, the F.D.N.Y. said. But Pirani said the number of calls does not give the whole picture.

“Yeah, there’s very few calls, but if there is a call, it can be very bad,” Pirani said.

Pirani is particularly concerned that many of the historic wooden buildings do not have fire alarms. Without alarms, it could take a while for security guards to notice a fire, especially at night when few people are on the island.

The Governors Island Preservation and Education Corp., which controls the island, declined to comment on the firefighting plan but released a statement about the fire alarms. The buildings did not have fire alarms before GIPEC took over in 2003, and GIPEC has put alarms in the buildings that are in use but not those that are unoccupied. GIPEC will install alarms in all buildings sometime this year.

Once someone on the island reports a fire, the F.D.N.Y. will direct Lower Manhattan fire companies to the Governors Island ferry, which docks at the Battery Maritime Building. After business hours, the firefighters will have to force a locked gate at the ferry slip, according to the F.D.N.Y. plan. The firefighters will then drive their trucks onto the ferry and head for the island, a seven-minute ride away. Once on the island, they will drive directly to the fire. If all goes well, that response will take 12 to 15 minutes, Pirani said.

But the ferry may not be available, or it may take too long to warm up. In that case, firefighters will drive to Engine 4/Ladder 15 on South St., leave their trucks there, and board a Brooklyn- or West Village- based fireboat from Pier 11, across the street from Engine 4. The fireboat will take the firefighters to the island, where security guards will meet them and drive them to the closed firehouse, which still has trucks and equipment. The firefighters will then drive the trucks to the fire. If all goes well, that response will take 20 to 30 minutes, Pirani said.

If no water transport is available, firefighters will drive their trucks into the Brooklyn-Battery Tunnel, which connects to the island via a ventilation shaft. Once firefighters exit the tunnel, security guards will meet them and take them to the equipment in the old firehouse. This option requires the most coordination and would likely take the longest, though the plan does not give an estimated time.

The Fire Dept. does not do drills of these scenarios but did do a walkthrough, an F.D.N.Y. representative told Pirani.

Once firefighters are on the island with trucks and equipment, their challenges are not over, and the biggest one will likely be water.

“Most hydrants are in service,” the plan states. “Low pressures and flows may be a problem.”

The plan recommends using a fireboat to pull in seawater to charge the hoses.

The plan also points out that most buildings on Governors Island are vacant, and since conditions are likely to be unsafe, it warns firefighters about the risks of rushing into the unoccupied buildings.

“When units arrive on the island, a fire may have been burning out of control for 20-30 minutes or more,” the plan states. “All members must be aware of construction features and the collapse potential of buildings in this condition. Units must be aware of the limited water supply provided by Governors Island hydrant system and adjust operations accordingly.”

The city committed to provide fire protection for the landmarked island in 2003, when the National Park Service gave it to New York, but the memorandum of understanding has no specific requirement to operate the firehouse or minimum response time standard.

While F.D.N.Y. officials have said they hope to reopen fire companies as the economy improves, it appears that the opposite will happen. Mayor Michael Bloomberg announced a grim budget last week, which included another $17 million in cuts to the Fire Dept. The Fire Dept. will meet the cut either by eliminating the fifth firefighter on 64 engines, a move unions have long opposed, or by eliminating one company in 16 of the firehouses which have both an engine and a ladder company. This would result in the permanent closure of Engine 4 on South St., which the current cuts closed only at night. The F.D.N.Y. has not identified all of the companies that would be cut under this scenario.